In general, a bicycle can travel in only one direction, that is, travel forward by pedaling forward, thereby causing fatigue in a rider's leg and uneven development in a leg muscle when the rider bicycles for a long time.
Thus, in order to solve the problems, many inventors have made an effort in the development of an apparatus for changing direction of driving force for bicycles which can be applied to a conventional one-directional pedaling bicycle.
The apparatus for changing direction of driving force for bicycles developed until now is classified into three fields roughly according to the methods adopted therefor, that is, methods using auxiliary gears, bevel gears and planetary gears.
As a representative invention related to the apparatus for changing direction of driving force for bicycles, Manrzoursos et al. (EPO Publication No. 0,369,925) disclose a system of bicycle motion transmission adopting auxiliary gears, Foster (U.S. Pat. No. 5,435,583) discloses a clutch operated, bidirectional, bicycle gear box adopting bevel gear and a clutch, and the invention of the same inventor of the present application(Korean Patent Application No. 98-1617) discloses an apparatus for changing power direction for bicycle adopting planetary gears.
However, because the above apparatuses are attached outside of the pedal shaft, the attached apparatus is protruding outside of a bicycle frame, thereby obstructing the pedaling of a rider. In addition, due to the protruding portion, it is difficult to attach the apparatus to a newly developed bicycle which can be folded for portability. Also the invention causes noise from engagement of ratchet gears which are indispensable for the inventions.
Thus, the above problems have raised requirements in development of a transmission for a bicycle, which can be attached to a shaft of a rear wheel and makes little noise, as an apparatus for changing direction of driving force for bicycles.
One of the example of such an apparatus for changing direction of driving force for bicycles, which can be installed on a shaft of a rear wheel, is Korean Patent Application 98-1616 of the inventor of the present invention.
Above invention discloses a driving direction changing apparatus of a bicycle hub, wherein a speed changing portion and a driving direction changing portion are installed, whereby it can transform the rearward pedaling to forward driving of bicycles and the speed of the bicycle.
However, the invention needs manipulation of a lever for transforming rearward pedaling to forward driving, more over, the invention can be installed only in the rear hub.